Mononykus, meaning “one claw”, is a genus of theropod dinosaur from the Late Cretaceous Period (70 Million Years Ago). It was discovered in the Nemegt Formation in Mongolia. The remains of the first discovered specimen consist of a partial skeleton lacking a tail. Only small skull fragments have been recovered as well. Later discoveries included the tail, which was relatively short, and a complete skull, which showed a unique toothless form. However, these newer discoveries have since been reassigned to the new genus Shuvuuia, and as such, Mononykus is detailed based on the dinosaur Shuvuuia.
Mononykus was about 3 feet long and had short, skinny legs. It was quick and nimble, running on two legs. This was a useful trait for the open desert area where it lived. The skull was small, and its teeth were small and pointed. Its diet most likely consisted of insects and small animals, such as lizards. It had large eyes, which allowed it to hunt at night. Its wrist bones were fused together like those found on birds. Each hand had one large (3 inch) claw (hence its name). Based on the short, stubby size of the forearms, it is even more likely that this dinosaur fed mostly on insects.
Mononykus is reconstructed with a covering of feathers. Some of its close relatives are covered in a downy coat, and given its lifestyle, it would seem Mononykus was feathered as well. The feathers would have been good insulation for the cool desert nights, and may have also acted as camouflage.